Text Fields

Bytes-based Fields

class pcapkit.corekit.fields.strings.BytesField(length, default=<pcapkit.corekit.fields.field.NoValueType object>, callback=<function _TextField.<lambda>>)

Bases: _TextField[bytes]

Bytes value for protocol fields.

Parameters:

• length (Union[int, Callable[[dict[str, Any]], int]]) – Field size (in bytes); if a callable is given, it should return an integer value and accept the current packet as its only argument.

• default (Union[TypeVar(_T, str, bytes, dict[str, Any]), NoValueType]) – Field default value, if any.

• callback (Callable[[Self, dict[str, Any]], None]) – Callback function to be called upon self.__call__.

pre_process(value, packet)

Process field value before construction (packing).

Parameters:

• value (bytes) – Field value.

• packet (dict[str, Any]) – Packet data.

Return type:

bytes

Returns:

Processed field value.

class pcapkit.corekit.fields.strings.PaddingField(length, default=<pcapkit.corekit.fields.field.NoValueType object>, callback=<function _TextField.<lambda>>)

Bases: BytesField

Bytes value for protocol fields.

Parameters:

• length (Union[int, Callable[[dict[str, Any]], int]]) – Field size (in bytes); if a callable is given, it should return an integer value and accept the current packet as its only argument.

• default (Union[TypeVar(_T, str, bytes, dict[str, Any]), NoValueType]) – Field default value, if any.

• callback (Callable[[Self, dict[str, Any]], None]) – Callback function to be called upon self.__call__.

String-based Fields

class pcapkit.corekit.fields.strings.StringField(length, default=<pcapkit.corekit.fields.field.NoValueType object>, encoding=None, errors='strict', unquote=False, callback=<function StringField.<lambda>>)

Bases: _TextField[str]

String value for protocol fields.

Parameters:

• length (Union[int, Callable[[dict[str, Any]], int]]) – Field size (in bytes); if a callable is given, it should return an integer value and accept the current packet as its only argument.

• default (str | NoValueType) – Field default value, if any.

• encoding (Optional[str]) – The encoding with which to decode the bytes. If not provided, pcapkit will first try detecting its encoding using chardet. The fallback encoding would is UTF-8.

• errors (Literal['strict', 'ignore', 'replace']) – The error handling scheme to use for the handling of decoding errors. The default is 'strict' meaning that decoding errors raise a UnicodeDecodeError. Other possible values are 'ignore' and 'replace' as well as any other name registered with codecs.register_error() that can handle UnicodeDecodeError.

• unquote (bool) – Whether to unquote the decoded string as a URL. Should decoding failed , the method will try again replacing '%' with '\x' then decoding the url as 'utf-8' with 'replace' for error handling.

• callback (Callable[[Self, dict[str, Any]], None]) – Callback function to be called upon self.__call__.

pre_process(value, packet)

Process field value before construction (packing).

Parameters:

• value (str) – Field value.

• packet (dict[str, Any]) – Packet data.

Return type:

bytes

Returns:

Processed field value.

post_process(value, packet)

Process field value after parsing (unpacked).

Parameters:

• value (bytes) – Field value.

• packet (dict[str, Any]) – Packet data.

Return type:

str

Returns:

Processed field value.

class pcapkit.corekit.fields.strings.BitField(length, default=<pcapkit.corekit.fields.field.NoValueType object>, namespace=None, callback=<function BitField.<lambda>>)

Bases: _TextField[dict[str, Any]]

Bit value for protocol fields.

Parameters:

• length (int) – Field size (in bytes).

• default (dict[str, Any] | NoValueType) – Field default value, if any.

• namespace (Optional[dict[str, Tuple[int, int]]]) – Field namespace (a dict mapping field name to a tuple of start index, and length of the subfield).

• callback (Callable[[Self, dict[str, Any]], None]) – Callback function to be called upon self.__call__.

pre_process(value, packet)

Process field value before construction (packing).

Parameters:

• value (dict[str, Any]) – Field value.

• packet (dict[str, Any]) – Packet data.

Return type:

bytes

Returns:

Processed field value.

post_process(value, packet)

Process field value after parsing (unpacked).

Parameters:

• value (bytes) – Field value.

• packet (dict[str, Any]) – Packet data.

Return type:

dict[str, Any]

Returns:

Processed field value.

Internal Definitions

class pcapkit.corekit.fields.strings._TextField(length, default=<pcapkit.corekit.fields.field.NoValueType object>, callback=<function _TextField.<lambda>>)

Bases: Field[_T], Generic[_T]

Internal text value for protocol fields.

Parameters:

• length (Union[int, Callable[[dict[str, Any]], int]]) – Field size (in bytes); if a callable is given, it should return an integer value and accept the current packet as its only argument.

• default (Union[TypeVar(_T, str, bytes, dict[str, Any]), NoValueType]) – Field default value, if any.

• callback (Callable[[Self, dict[str, Any]], None]) – Callback function to be called upon self.__call__.

__call__(packet)

Update field attributes.

Parameters:

packet (dict[str, Any]) – Packet data.

Return type:

Self

Returns:

New instance of _TextField.

This method will return a new instance of _TextField instead of updating the current instance.

Type Variables

pcapkit.corekit.fields.strings._T: str | bytes | dict[str, Any]